On top of that, he discovered evidence that two different banks — a small, community bank and a large, top-10 bank — have bought back their customers' stolen cards, he says.

Now he believes he's found the real life identity of a Ukraine man that has, Krebs alleges, been involved with various underground markets that sell stolen credit cards. He's even engaged in an online chat with the person, while also admitting that he has no idea if this particular guy "was involved in hacking Target," Krebs writes, adding, "but it's a good bet that he at least knows who was."